Preservatives microbiological contamination

Pigment slurries are one of the major components in paints and coatings that contribute to or affect the performance of a formulation. The nature of pigment slurries makes them extremely susceptible to microbiological contamination that can degrade the final formulation. Often biodeterioration can be prevented with plant sanitation and the use of a preservative, but formulators must not rely on the precept that a particular preservative that works today will always remain effective down the road. In complex environments, contaminants can enter the system at different points, or a formulation change may render the original preservative less effective. Manufacturers must remain aware of trends in the industry to ensure their products are properly protected. 

The choice of process depends on the level of microbiological contamination of the raw materials and packaging, and the ability of the product to withstand growth of micro-organisms (e.g. preservative levels and sugar content). Also of great importance is the ability of the product to withstand heat. 

The final check on purity is on the finished product. The high water content and the inclusion of nutrients for unwanted microbiota make cosmetics subject to microbiological contamination. Thus, topical OTC products and cosmetics require preservation and a final check before distribution. Preservative systems and GMPs usually ensure delivery of essentially uncontaminated cosmetics. The microbiologic requirements recommended by the CTFA include the following ... 

Microbiological protection of multiple-dose presentations such as liquid inhalations, nasal sprays, oral liquids, creams, and lotions is more complex. Once opened they are susceptible to microbiological contamination. If they are aqueous-based, they are in principle susceptible to proliferation of these new contaminants. To avoid this, they are formulated with antimicrobial agents or preservatives and are expected to be able to comply with preservative efficacy standards specified in the pharmacopeias. Preservative efficacy tests (not harmonized) are described in Section 51 of the USP and Section VIII. 14 of the PhEur (Fig. 3). 

Microbial growth—certain adhesives (starches, dextrines) can support microbial growth, hence either preservatives will need to be incorporated or procedures used to minimise microbiological contamination. 

Aqueous nasal drops and nasal sprays are preserved when they are supplied in multidose containers. In order to get a low level of microbiological contamination at the start, the use of sterilised water or sterilised solutions of preservatives as primary materials is recommended. 

Microbiological stability may be a problem too. Aqueous enemas are prone to microbiological contamination and growth. The Ph. Eur. sets the same requirements for TAMC and TYMC (see Sect. 19.6.3) to rectal preparations as to oral preparations (10 CFU/g or mL, see Sect. 19.6.2). Enemas, like oral mixtures, should also meet with the requirements of preservation efficacy. For preservatives reference is made to Sect. 23.8. Generally methyl parahydroxybenzoate 0.15 % is used. 

Preservatives are substances that, usually in low concentrations, are added to preparations because of their antimicrobial action. Adding preservatives is one of the methods to keep the microbiological contamination of... 

Duddridge, J. E., 1987. Problems associated with microbiologically contaminated mains water. Preservation Towards 1990 and Beyond, Conference at Ladbroke Hotel, Warwick, UK, 11/12 June. 

A major concern in the preparation of cosmetic, toiletry, or chemical specialty products is adequate preservation against microbiological contamination. Such contamination can arise from many possible sources, such as ... 

An entirely different type of contamination arises from the presence of microbiota in a product. As in the case of chemical contamination, compendial requirements for microbiological purity exists. Pharmacopoeial standards vary from country to country, and manufacturers must use the specifications and kill times that meet local requirements. As of this writing, the criteria in the British Pharmacopoeia are more stringent than those estabUshed by the CTFA, which are stricter than those in the United States Pharmacopoeia. In order to meet commonly accepted standards of microbial purity, manufacturing faciUties must be periodically cleaned and all products that can support microbial growth must contain an effective preservative (6). 

Pharmaceutical manufacturers may justly argue that their responsibility ends with the supply of a well-preserved product of high microbiological standard in a suitable pack and that the subsequent use, or indeed abuse, of the product is of little concern to them. Although much less is known about how products become contaminated during use, there is reasonable evidence that continued use of such products is undesirable, particularly in hospitals where it may result in the spread of crossinfection. 

---